This incredibly fast 400mm lens abounds in special-and unique-features. Because of a special cam focusing system, not only is the lens shorter, smaller in diameter and lighter in weight, but it focuses "faster" at close distances and "slower" at longer distances, for improved handling. And because the focusing is internal, the lens stays the same length even at close focuing distances. Naturally, its optical quality is strickly professional-caliber all the way, and for the serious photographer who needs length, speed and sharpness, there is no finer lens. SPECIFICATIONS Type: super telephoto Construction: 6 elements in 5 groups Angle of view: 6 degrees 10 minutes Minimum Aperture: F/22 Closest Focusing Distance: 13ft Filter size: 34 drop-in with holder Lenshood: built-in Length: 11 1/8 in Weight: 2lbs 14oz.